1. Field of the Invention
This invention relates to an apparatus and a method for packaging semiconductor devices and, more particularly, to an apparatus and a method in which die bonding, wire bonding and resin molding operations are sequentially carried out so that the semiconductor dies cut from the wafers are provided with leads and sealed into a resinous package.
2. Description of the Prior Art
In the production of semiconductor devices such as integrated circuits and transistors, semiconductor wafers on which circuits are formed in the previous steps are cut into individual chips or dies, and each die is then provided with leads and a package. In one of the processes for providing semiconductor dies with leads and a package, the following steps are taken. First, the dies are picked up from the cut wafer by a die sorter so that each die is positioned on the precise location for the die in successive patterns formed in lead frames and is bonded thereto. Second, the electrodes on each semiconductor die are coupled to the leads of the patterns formed in the lead frame by means of thin gold or aluminum wires in a wire bonding process. Third, the dies, each of which has been electrically coupled to its respective leads of the lead frame, are molded and sealed into an epoxy or a silicone resin package by transfer molding equipment, together with predetermined portions of the lead frame.
FIG. 1 shows a typical prior art apparatus for performing such packaging of semiconductor dies in a continuous operation. The apparatus comprises a die bonder unit 1, a pair of wire bonders 2a and 2b, a molding unit 3, and a pair of buffers 4a and 4b, which are disposed between the die bonder unit 1 and the pair of wire bonders 2a and 2b, and between the pair of wire bonders 2a and 2b and the molding unit 3, respectively. Except for the portion for transferring the works (i.e., the lead frames on which semiconductor dies have been bonded), the molding unit 3 is partitioned from the rest of the apparatus by a wall 5, which prevents the dust generated in the molding process from contaminating the semiconductor dies during the die bonding and wire bonding processes The die bonder unit 1, the pair of wire bonders 2a and 2b and the molding unit 3 perform the above-described first, second and third steps, respectively, of the packaging operations of the semiconductor dies. The pair of buffers 4 a and 4b, on the other hand, temporarily store in progress the work to adjust for the time lags caused by differences in the times required in the die bonding, the wire bonding and the molding processes, respectively.
The conventional apparatus for providing semiconductor dies with leads and a resinous package as described above is capable of producing a large quantity of a single kind of semiconductor devices with great efficiency. However, the separation of the molding unit by a partition wall from the rest of the apparatus and the disposition of the buffers for the compensation of the time lags in the production line results in a larger size of the apparatus. Thus, the conventional apparatus required a large space and a great cost for the installation thereof, and is uneconomical and unsuitable for the production of small quantities of various types of semiconductor devices.